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When approaching a stall, is the first priority to apply power or lower nose?
I’ve always wondered. And I’d assume it’s the same regardless of aircraft? But when approaching a stall would the main priority be adding more power?
I ask because what if a crew was on final for landing and approached a stall, the rear end is dropping and the nose is rising. I feel like the flaps at their current position during landing, would only make matters worse? And applying power could make more lift with a poor angle of attack?
Would a crew lower the flaps in that situation, after applying more power and pushing the control columns forward?

You may consider that acting on the stick leads to quicker reaction than acting on throttle. Pushing the stick can lead to elevator full deflection ina fraction of second and to reduced AoA in less than a second while an engine can take several seconds to spin up

I'd also add that in a power-on stall, the only recovery available is to lower the nose since you're already at full power.

The instinct drilled into a pilot's head from the beginning as the primary response is "lower the nose" to lower AOA.  If you learn in a glider, that's the only option, so it's easy to drill the instinct into peoples' heads (one reason that glider training before power is so good for pilot skills later).  In a power plane, it's lower the nose and add as much power as you need, but lower the nose must be the first instinctive action.  How much to lower the nose depends...
In a non FBW jet (FBW is another story, the computers taking care of things on your behalf whether you want them to or not), the stall training you get for low altitude stalls (you don't get to an actual stall - you start from stick shaker onset) is lower the nose but not too much, add thrust to maximum, and regulate the pitch attitude to stay just above stick shaker onset (just above the speed tape's "barber pole", the red broken band that indicates the stall region) and if flaps are at landing setting, call for retraction to go-around flap once you have stopped descending and are accelerating with decent speed margin above shaker.
The objective is to minimize the altitude loss as you recover airspeed.  At shaker onset you still have some margin above the actual stall and if you're close to the ground you don't want to dive, so you just tease the pitch to hold it on the edge of shaker.  You will generally use this procedure for any stick shaker event in denser air, below, say, 10000 or 15000 ft.  As a general rule, you do not make configuration changes with gear and flaps until you have got yourself in a good situation energy wise (not sinking, accelerating - although there may be variations from a/c type to type) because retracting flaps can increase your sink rate and the standard procedure with gear is not to retract until there is a positive climb rate.
At high altitudes, especially above 30000 ft, the stick shaker recovery method is much more aggressive and you are trained to actually push over enough to lose several thousand feet and not be concerned with altitude loss. In the thin air the practice of teasing the pitch to stay just above shaker doesn't work so well, because the air is thin but the inertial mass of the machine is unchanged and that can get you into trouble if you fly it the way you do down low.  You can find yourself back into the shaker/pusher/stall break region if you work the pitch to manage AOA on the edge of shaker the way you would close to the ground.
One of the events that lead to special high altitude stall recovery training during recurrent training was this famous (within the business) Pinnacle Airlines incident with a CRJ200 (quite a harrowing read; I don't think it was mentioned in the report, but the post crash fire was caused when they slid into a back yard garage with a meth lab in it).

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The other answers have already correctly stated that lowering the nose is the first action, and that you do not fiddle with the configuration when stalled.
I'd like to add a point relating to smaller propeller aircraft: when flying at the edge of stall, or even stalled (some GA planes are surprisingly docile even under full stall), you do not want to suddenly push full power. Why not?
Your control authority is not at it's best. Controls feel "mushy", and the aircraft response is sluggish. If you suddenly bring into the game significant torque from the propeller, P-factor, slipstream starts pushing tail to the side... instead of getting out of the stall, you may very well have departed controlled flight, and are now spiraling towards ground with a hig power setting.
So: first secure control of the aircraft, then minimize altitude loss with power.

The priority is to unload the wings: which means lower the G load on the wings because the stall speed increases with higher G loads and reduces with lower G loads until reaching 0 with 0 G. So an aircraft can stall at any speed really, it all depends on the G factor it is subjected to.
That's why when you stall the first thing you should do is to lower the nose which means lower the AOA which means unload the wings which means reduce the actual stall speed which means get it as far as possible from your actual speed. The added power is used to reduce the loss of altitude during recovery which can be life saving if you are close to the ground.
Adding power on a below wing engine aircraft like the B737 can be dangerous because of the pitching moment the sudden add of thrust can generate which can make you stall again.

Or overshoot the nose down and let the engine pitch bring it back up. I had that happen on an A320 in approach to OAK, suddenly the nose went up 15 degrees, went down 20, spoolup, and back to normal. Near as I can figure it was a bit of windshear.   Anyway, I'm sure that engine pitch could be easily corrected with some sort of trim system, so inconsequentially you wouldn't even need to train the pilots. What could go wrong?

The priority is to reduce the AoA. This can be done in several ways (changing the attitude by lowering the nose, changing the chord line by lowering the flaps, thus reducing the effective AoA, increasing the airspeed by opening the throttle, thus lowering the effective Aoa...)
The choice depends on the flight conditions, and it's the pilot's choice...

[img]https://i.imgur.com/zrDvJIz.png[/img]

https://imgur.com/zrDvJIz

When you lower flaps, the automatic reaction is (usually) that the nose pitches down. The net effect of lowering flaps is thus a reduction of the AoA.

You are on final, you drop flaps, and in order to keep the glide path, lift can't be allowed to rise. As the airspeed is more or less constant, the only way of compensating the higher coefficient of lift derived from the lowered flaps, thus keeping lift constant, is to reduce the AoA pitching the nose down. In most cases that I know, it's an automatic reaction of the plane, that was trimmed for no-flaps...

While that last comment is certainly completely true AFAIK, it seems to me you're answering a question different than what was asked. As such, I can't argue with it.


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How does MCAS communicate with other systems to know if the flaps are retracted or not?
How exactly does MCAS communicate with the flaps setting to know if the flaps have been retracted?
I just noticed on the preliminary report for ET302, the flaps were set at 5 degrees. It doesn’t say when or if the pilots retracted them completely. So I’ll assume the flaps were at 5 degrees the entire flight. So it makes me curious about these systems communicate, if I understand correctly, MCAS and everything was perfectly fine, the only faulty part was the AoA, so there shouldn’t have been a problem with the systems determining whether or not flaps were set.

Probably it doesn't. In the real world assumptions do exist.

I don't know how the 737 does things.  In other airplanes, there is a position sensor at different degrees that is sent to a flap control computer.  The position sensors may be at 3° and 7°.  If the 3° sensor is active but not the 7° sensor, it would be assumed the flaps were selected to 5°.  The flap control computer makes that determination and then communicates that position to any other system that requires it.

Airliners built since the 70s us the ARINC 429 databus standard for intercommunication of black boxes https://en.wikipedia.org/wiki/ARINC_429. So when flaps are at a given position, it will set a bit on a particular data word on he bus, and MCAS can read that bit off the bus and know where the flaps are. Not quite sure of the MAX is using that standard or something newer, so not posted as an answer.

MCAS is implemented on the Flight Control Computers (FCCs). The FCCs communicate over an aviation data bus, ARINC format. The B737NG used ARINC 700 series standard for communication - sensor information is linked to the FCCs via the avionics data bus. The B737MAX may or may not use a later standard ARINC bus.
There are two FCCs on the B737MAX. From this link:

Computer redundancy. As of 2019, the two flight control computers of Boeing 737 never cross-checked each other's operations; i.e., each was a single non-redundant channel. This lack of robustness existed since the early implementation and persisted for decades. The updated flight control system will use both flight control computers and compare their outputs. This switch to a fail-safe two-channel redundant system, with each computer using an independent set of sensors, is a radical change from the architecture used on 737s since the introduction on the older model 737-300 in the 1980s. Up to the MAX in its prior to groundings version, the system alternates between computers after each flight.[191] The two computers architecture allowed switching in flight if the operating computer failed, thus increasing availability. In the revised architecture, Boeing required the two computers to monitor each other so that each one can vet the other.

So not only do the FCCs know if the flaps are retracted, they now know if their computations correlate.

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ETH 409: Was the most obvious sign of fatigue being a factor due to one of the pilots calling out “go around” when they were climbing after T/O?
One of the pilots yelled out “go around” x6. It looks like they were making a right turn when they should have been making a left turn. The controller informed them for the second time to turn left, and that’s when the callout happened. Is this the most obvious reason for fatigue being a contributor to the accident?

Have you read the full accident report? Your questions suggest either you did not read the report, or you have a poor understanding of the report. https://www.bea.aero/docspa/2010/et-b100125.en/pdf/et-b100125.en.pdf

I fail to understand what you are asking for. are you asking "what are the elements making the investigator think fatigue is a contributing factor?", "what were the most obvious signs of fatigue?" or "how much did fatigue contribute to the accident?" or something else. You may consider editing your question to clarify it.

@MikeSowsun no, I have not. Only a short small clip that gave me this info, and with no luck in searching I came here.

@ManuH I’m asking if the pilot repeating “go around” was what led them to think fatigue played a role here? Or did he mean go around like the other way? The only time I’ve heard such words is when the plane is landing.....so I’m just wondering

@Firefighter1 you should put your last comment in your question. It would help clarify it.

The "Go Around" call was a call for a particular power setting (TOGA) because the aircraft was in a stall condition (rapidly decreasing airspeed, high AoA and stick-shaker). This was not fatigue by the aircrew thinking that they were actually performing a "go around", the captain wanted full-power out of the engines and there is a button that does that.

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Does ELMS inhibit cabin pressure alarms on the 777, and would the MEC Override Vent be stuck open following an electrical failure?
I found this article rather interesting, but like most things on the internet, they can be wrong. I couldn't think of a better site to address this question. This user says:

when ELMS takes over power supply it shuts down the Air Cycle Machine (ACM) and the Air Supply Cabin Pressure Controller (ASCPC). Cabin pressure alarms in the cockpit also lose power.

The user follows up with this later on:

In addition to loss of electrical power from the cabin pressurization system electrical smoke in the Avionics Bay or MEC likely tripped open a vent called the MEC Override Vent, which simply allows electrical smoke to be pushed out by cabin air pressure. Once open this vent needs electrical power to close again, so if an electrical failure followed, it would be left limp and open.

I look forward to reading your answers about this, Thank you!

Generally, the post you quote from does not look like a credible source. For starters, it says things like:

Electrical failure shut down the Air System Cabin Pressurization Controller (ASCPC) and Air Cycle Machine (ACM) which on a Boeing 777 are all electric. Unlike most other airliners the B777 does not use engine bleed air.

This is completely wrong. The 777 uses engine (or APU) bleed air to operate the PACKs. The author might have mixed this up with the 787, which uses electrically powered compressors for cabin pressurization instead of bleed air.

Bleed air can be supplied by the engines, APU, or a ground air source.
Bleed air is used for:

air conditioning
pressurization [...]

(Boeing 777 FCOM 2.40.1 - Air Systems - Bleed Air System Description)

The vent in the electronics bay exists and it will indeed open automatically to vent out smoke:

The forward system reconfigures automatically to an override mode when:

[...] smoke is detected in the forward equipment cooling system or the forward equipment ventilation system [...]

In the override mode when the FWD CARGO FIRE ARM switch is not ARMED, the vent valve opens, both supply fans shut down,
and the forward cargo heat valve closes. [...] Cabin differential pressure draws air through the flight deck panels into
the E & E equipment compartment to create a reverse flow of air across the equipment, then through the override valve
to an overboard vent.

(Boeing 777 FCOM 2.20.12 - Air Systems - Air Conditioning System Description)
With an electrical failure it is plausible that this valve could no longer close, therefore preventing cabin pressurization.

The ELMS (Electrical Load Management System) described in the post will shed loads in this order:

The load shedding is galleys first, the utility busses. Utility busses are followed by individual equipment items powered by the main AC busses.

(Boeing 777 FCOM 6.20.1 - Electrical - System Description)
The FCOM indeed does not specify the order of these "individual equipment items". Since we don't know what exact failures occurred on MH370, it is impossible to say which systems were shut down. However, during normal operation there are two AC busses (left and right) powered individually. No single point of failure could shut down both PACKs.
The post further claims that

Cabin pressure alarms in the cockpit also lose power.

This cannot be related to the ELMS, which only controls the AC power distribution. The EICAS alerts are however powered by the DC system (via the flight instrument busses), which can be powered independently of the AC busses in standby operation:

The main DC electrical system uses four transformer-rectifier units (TRUs) to produce DC power. The TRUs are powered by the AC transfer busses. [...]
The standby electrical system can supply AC and DC power to selected flight instruments, communications and navigation systems, and the flight control
system, if there are primary electrical power system failures.
The standby electrical system consists of:

the main battery
the standby inverter
the RAT generator and its associated generator control units
the C1 and C2 TRUs.

(Boeing 777 FCOM 6.20.13 - Electrical - System Description)
The author of the post further claims that no warning is given to the pilots because the SMOKE / FUMES REMOVAL checklist in the QRH (linked in the post) shows UNANNUNCIATED. This is however the wrong checklist for the case described earlier. The unannunciated here means that this checklist is for when the pilots recognize smoke or fumes in the flight deck before any annunciation. The correct checklist for the open vent in the electronics bay is this one (and it is annunciated on the EICAS):

[] EQUIP COOLING OVRD
Condition: The equipment cooling system is in override mode.

Wait 2 minutes. This allows time for any smoke in
the system to clear.
EQUIP COOLING switch . . . . . . . . Off, then AUTO
The EQUIP COOLING OVRD message blanks.
Wait 1 minute. This allows time for the system to reset.
Choose one:

EQUIP COOLING OVRD stays blank: ■ ■ ■ ■
EQUIP COOLING OVRD shows again:
Note: After 30 minutes of operation at low altitude and low cabin differential pressure, electronic equipment and displays may fail.

(Boeing 777 QRH 2.19)

Another weird claim from the post is:

The brand new Boeing 777X model suffers the same vulnerability.

I wonder how the author wants to know this. The 777X is not in service yet and the author claims to be an aviation enthusiast from New Zealand. Only a Boeing engineer could possibly know about such system details of the 777X.


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Are there any characteristics of a hypoxic flight?
Any patterns that investigators look for? For example, what happens when the engine flames out? is it guaranteed to enter a high speed dive? And would this affect certain parts of the aircraft, causing them
to separate under torsion and not compression?

By “hypoxic”, are you referring to the pilots? Why the mention of engines flaming out and high-speed dives?

Although, I have not heard the terms hypoxia and hypoxic applied to aircraft engines, I assume you are asking about engine failure due to a lack of oxygen. How would this be any different than any other engine out scenario? Except for situations where the airspeed is below Vmc, or if the effects from asymmetric thrust go uncorrected, there is no reason to cause the aircraft to go into an uncontrolled descent. The glide ratio may be affected by the thinner air. But, the glide down to a lower altitude would still be possible.

If you are referring to an unconscious pilot slumping over the controls of an otherwise functional aircraft, I guess it would depend on how loose his/her seatbelt is. If they are not applying pressure to the controls, the aircraft may remain stable for a considerably long time. If the autopilot were on, the aircraft could remain airborne until it ran out of fuel. Even after it runs out of fuel, it may still remain in a flying attitude (stable glide) all the way to the ground.

@StephenS I’m asking because the engines will flame out eventually with everyone dead. Is there something investigators can clue together by the way hypoxic flights end? The ATSB listed MH370 in 2015 under hypoxic characteristics and listed many reasons but one being a high speed dive

If a "ghost" airplane with passed out pilots is unattended and the engines flame out, what is likely to happen is it will fly along on autopilot until one engine flames out a few minutes before the other. This will impose a pretty large amount of yaw, which the airplane's yaw damper may or may not have enough authority to counteract.  Yaw dampers generally can move the rudder somewhere around 1/3rd of normal travel and aren't meant to cope with asymmetric thrust (I recall from recurrent training in the CRJ that a flameout in cruise still required more rudder than could be applied by the YD to keep it flying straight and you still had to get your feet on the pedals post haste).
With the one engine dead, the yaw damper will be at full travel trying to "center the brick" (the little box shaped skid indicator on the Primary Flight Display), and if that's not enough, the airplane will be skidding along trying to roll into the dead engine, and the autopilot will be applying aileron to try to keep the wings level, and the airplane will fly along cockeyed, like happens when a new pilot on the type course experiences his/her first engine cut and forgets about their feet.
The amount of aileron may cause the autopilot to kick off at some point, at which point the airplane will immediately roll off toward the dead engine into a spiral dive (they won't just dive straight down, they have to roll off to one side into a spiral where the airplane's natural speed seeking pitching tendency just causes it to wind up the turn tighter and tighter as it goes steeper and steeper and faster and faster).
Or, if the autopilot is able to hang on, eventually the other engine flames out, the ram air turbine drops, most electrical services are terminated except emergency ones and the autopilot is likely to kick off then.
At that point, if the airplane is trimmed nicely and the air is smooth, it will likely simply descend more or less straight at its existing trim speed in a straight ahead glide... until something disturbs it, like a bump that makes it bank a bit more than dihedral effect can accommodate.
At that point most airplanes will drift off slowly into a descending spiral. It will turn steeper and steeper and descend faster and faster, either until bits start to come off the airplane from overspeed/over G, or it hits the ground (bits raining from the sky following spiral dives is what usually happens in GA disorientation events in instrument conditions - think Kennedy's crash).
So in the end, one of two things will happen.  If the airplane was trimmed at 240kt indicated, it will fly into the ground straight ahead descending at 240kt, or, if it got bumped into a spiral, it will come nearly straight down at close to Mach, making a small crater, or come down in individual pieces after breaking up on the way down.
And ending like the Lady Be Good is unlikely with a jet.


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Do MD-11 pilots ever use flaps 50?
I'm curious if there is ever a purpose to use full flaps like that? Was it a bit of an overkill?

Flaps 50 vs. Flaps 35 results in approximately a 5 knot reduction in approach speed in calm conditions.
I routinely use flaps 50, depending on weight, runway, and conditions.

I'm curious, do you have training material or other resources describing procedures with those different settings?

I'm not sure what the procedure is that you're looking for.  The flap setting will depend on the weight, runway length and elevation, temperature, surface condition, etc.

Volume IV of the MD11 FCOM (operating manual) is the performance volume, and contains 398 pages of charts and data.  My material is all on an ipad and not in an exportable form.  I use a program on the ipad for runawy data analysis for takeoff and landing information (TOLD data).  We do have guidance on flap setting in most large aircraft, which is the minimum flap necessary setting for the conditions, and there's always other considerations such as windshear, go-around, etc, as well as increased noise during the approach with a high flap setting (more power required), higher fuel burn, etc.

As noted above, the MD11 has the highest approach speeds of any commercial airliner.  Greater flap settings mean the potential for more damage to the flap structure, as well.  We do have an operational policy that if landing weights exceed 204,000 kg and the landing field is less than 8,500' long, we use flaps 50, and Medium or Max autobrakes (the exception being if weight is less than 181,000 kg, we only use minimum autobrakes to avoid damage to wheels and gear (specifically center landing gear drag link).

@Will Integrate these comments into the answer, and you'll have something worth reading. Comments are ephemeral.

@Will I'm referring at procedure from which you extract those numbers you put in your answer. If it adds relevant information, you should include it in your answer.


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How does a DC-10 flight engineer manually raise the cabin altitude?
Reading into Federal Express Flight 1406 and I noticed when the flight engineer said he was raising the cabin altitude “manually” I assume this has something to do with cutting off the oxygen, but how can it be done manually? This also makes me curious to know if there is another way of doing it, but would be disabled under certain emergency scenarios?


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Is there a penalty for changing the approach procedure after accepting one?
For example: If you request a visual approach and get approved, but you meant to request an ILS approach, are you not allowed to change it?
Is there some type of penalty for changing approaches after you've already received one?
For example in the video, "PilotsEYE.tv - A380 Landing KSFO San Francisco", the copilot misread a visual approach as ILS, and was given the ILS, but despite the captain's disapproval, they didn't make another call requesting the change.

There is no penalty per se, but visual approaches in particular have lower separation requirements, so having to switch you back to a non-visual approach may require ATC to make corrections (e.g. delay vectors, speed control or, in extreme cases, a missed approach), which may feel like a penalty.

This is only true in the US. In most cases, the separation minima are the same regardless of the type of approach flown.

Hello, I accidentally reversed the approaches! I just re edited. In case you wanted to make changes to your answer, I apologize!

@MichaelHall It was clumsy wording, and the question has changed significantly since it was posted.  In any case, the point is that once the tower was agreed on and planning for a visual approach by the aircraft it's less hassle and less confusion for everyone if they simply follow through with that rather than changing their mind shortly afterwards.

It's no problem, just tell Approach you have the airport in sight & request the visual. They'll give it to you almost always. A visual approach is generally a little less restrictive for the controller than an instrument approach is.


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Is autorotation possible from a 0 rpm start at high altitude?
I am working on an enclosure that is to be ejected from a rocket at apogee (10,000') and fall to a target altitude at a descent rate below 20ft/s before releasing its payload. The idea is to have coaxial rotors with collective pitch control deploy and autorotate to slow the descent of the enclosure and payload.
My question is how I can start autorotation with blades that have essential zero angular momentum, and are there special considerations for the use of coaxial rotors?

Go back to Estes rocket days.  There is a whole class of competition rockets known as "heliroc" or helicopter recovery.  These ascend like a conventional rocket, in a vertical(ish) path and fin stabilized; at (or near) apogee, they release a rotor by some means and the rotor spontaneously begins to autorotate, often giving a lower descent rate than a parachute.
Go even further back: look at maple seeds (aka maple keys).  They autorotate so efficiently that they'll enter stable rotation and constant (low) sink rate in as little as one blade length of fall (they do have very low wing loading, however).
So, yes, it's possible for a rotor disk to spontaneously begin autorotation from a dead stopped starting condition.  Mother Nature does it billions of times every autumn, and school children do it thousands of times every year.
Yes, this will work with a coaxial rotor, if you can keep the rotors from interfering with one another during deployment (for instance, by braking them until fully deployed).  However, since there's no reaction torque from freewheeling, autorotating rotors, there's no reason to have coaxial rotors.  It's far simpler to use an ordinary rudder for yaw control than differential collective, and you'll have half as many parts for pitch and roll.

Are there any special considerations needed for coaxial rotors?

That depends on how you deploy the rotors.  If they're folded along the rotation axis (i.e. flap hinge folded) and can be deployed simultaneously enough to prevent one rotor interfering with the other, it shouldn't matter.  BTW, you do know there's no torque reaction during autorotation?  That makes coaxial rotors and unnecessary complication.

The current idea is the have the blades folded "down" along the rotational axis. The reason I was considering coaxial rotors is that one of our design goals is to generate electrical power during descent. If I am not mistaken, a single rotor connected to a motor would have torque. Could I use a single rotor and vanes to keep the enclosure from rotating?

Pulling energy off the rotor for electric generation will produce a torque drag (opposite direction from torque reaction), so you'll need some means off offsetting the torque.  Vanes would have to be large, since your speed is low.  Might be lighter to put a rotor-driven tail rotor on it.  Deployment setup is left as an exercise...  ;)

...how I can start autorotation with blades that have essential zero angular momentum...

By using the collective pitch control mentioned in OP. At release, the blades should be aligned with the free stream like a feathering propeller, then gradually be set with decreasing blade AoA as the rotor speeds up.

...are there special considerations for the use of coaxial rotors?

Yes, coaxial rotors complicate all design efforts tremendously. Both rotors would have to have blade pitch control, one blade shaft must be mounted within the other which counter-rotates, etc. Much simpler to use only one, larger rotor, since yaw compensation is not required during autorotation.
Note that at vertical autorotation, a rotor has a slightly lower drag coefficient than a flat plate of equal area, which has a lower drag coefficient than a parachute. As mentioned in this answer.

Thank you for the advice! A design goal I did not mention in the OP is power generation during descent. Keeping the net torque = 0  is the reason I was looking at coaxial rotors in the first place.
If I were to go with a single rotor, are there methods of providing counter-torque such as vanes (no including a tail rotor), and would 4 blades have advantages over 2 blades? Again, I appreciate your input and would appreciate sources to self educate if you know of them!

Ah OK. When the tail rotor of a single rotor helicopter fails, the engine is idled and the helicopter autorotates back to earth: autorotation causes close to zero shaft torque. Which also means that zero shaft torque can be used for power generation... Note that this sort of autorotation delivers blade lift which slows down the deceleration from gravity. If a propeller is just windmilling, it creates shaft torque and no lift, and indeed does require yaw compensation, via simple adjustable vanes for instance.

A good book for self education is Principles of Helicopter Aerodynamics by j. Gordon Leishman, with a chapter on windmills as well.


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How common is an airliner activating reverse while still in flight?
Around 1977, I watched a DC-9 landing at Guacimeta airport, Lanzarote, Canary Islands, Spain, opening the flaps reversing thrust of both engines just over the airstrip end, but some 9 feet over the ground. Of course, it fell down that height as fast as a stone. Is this usual?

The previous question was rather theoretical: What if? but this refers to an actually watched case. The underlying subject is the same, yes. It's up to you mixing or fusing both. Thanks. Salut +

Well, you ask whether it is common. The other question answers that one. The answer here should be clear: This is very, very unusual.

The system will allow deployment based on various criteria, and radio altitude height may be one of them, so even for a system not designed to operate "in flight", you still can deploy the TR's a few feet off the ground. Pretty ugly, rough touchdown when you do, though, and certainly not advised. How often that happens would be speculation, but probably very rare.

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The principle in 'Trompe' is applied to airplanes?
'Trompe' (see Wikipedia) is a water-powered air compressor, commonly used before the advent of the electric-powered compressor. A trompe is somewhat like an airlift pump working in reverse, used to provide compressed air for bloomery furnaces in Catalonia and USA. By sending a fast water flow through a duct, a pull effect on air is obtained.
I wonder if a pure Turborreactor working inside a larger Duct, with no Low Pressure Fan, would have same efficiency, with less parts, as a high Bypass Ratio Turbofan. Operation inside duct, or even inside fuselage, would result in reduction of sound and thermal prints. Salut +

Hint: compare weight of a trompe to that of a conventional pump to produce the same volume and pressure of air.

You are basically describing an ejector pump. This would not be very efficient, I'm afraid (I'll try to dig up some comparative figures).
The arrangement in this case would be a jet engine used to accelerate an amount of air inside a duct. With a long enough duct, the end result would be a single airmass exiting at (somewhat) uniform speed. Unfortunately, because energy must be conserved, the kinetic energy of the air exiting the apparatus would not even match the kinetic energy of the air exiting the jet engine, because of turbulence, skin friction of the duct etc.

My doubt came from the fact that behavior of a high speed hot jet differs from that of a large fan moving higher mass at lower speeds, and that the Trompe is somehow similar to the Dyson home fans, cited elsewhere in this site, that seem having good efficiency with low energy use. If same amount of air can be moved with a low speed fan and with the Trompe arrangement, reaching an overall efficiency close to a high bypass ratio Turbofan, you save a lot of weight and parts susceptible of failures, besides 'Stealthyness'. Was this ever tested? Thanks. Salut +

The Dyson fans use this principle, there is a discussion about it here in Aviation Stack Exchange. Blessings +


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What's the difference between Stress and Strain?
There's a book for Engineers, entitled: 'Roark's Formulas for Stress and Strain', some describe it as 'High level Mathematics'. So what?

Stess = tensión. Strain = deformación. But this is not exactly an aviation question.

This is a pure physics question and should be asked on physics.stackexchange instead.

No, the book cited is for aeronautical engineers. Thanks. Salut +

@Urquiola what makes you think that structural mechanics in a plane are different from those in a bridge? Or algebra? Or general physics? Roark, Timoshenko, Fung, etc are part of the recommended bibliography for many engineering programmes, be they Mechanical, Civil or Aeronautical.

Despite the fact that the book is for aeronautical engineers, this is a physics question, not an aviation question. After all, aeronautical engineering involves physics.

You are wrong, question deals with aeronautics, at least with design and materials, but as the question already had a very good response, I won't accept a quarrel with you. Gesund +

Stress is the load divided by the cross section of the material bearing it, and is expressed in units of pressure.
Strain is deformation divided by the original dimension in the direction of the deformation, and therefore is dimensionless.

Underneath the formal definitions, the intuition is

stress is what you do to a material;
strain is what it does as a result.

To a first approximation they are connected by Young's modulus, which obviously varies a great deal by the material.
You can put two materials under the same stress (one industry standard elephant, say) and the the strain will be very different depending on the material (steel might exhibit less strain than rubber, for example).
Alternatively, the same strain (eg 10% lengthening) is achieved with different stresses depending on the material (eg stress of one mouse per square inch for rubber, stress of one elephant per square inch for steel).
As you can tell from the intuition above, stress is measured in pressure (force per area) and strain is dimensionless (just a proportion or percentage, or whatever).

Stress is the cause and strain is the effect... And stress/strain is Young's modulus, that is a measure of the impedance of the material. In the same way as, in electricity, impedance, as a general term for resistance, is tension/current, i.e., cause/effect...

I don't think I can agree with this answer. Sometimes what I do to a material is stretch it to a particular length, and what it does as a result is exert a particular amount of tension. Tuning a guitar is a good example of this, I think: you adjust the strain in order to produce the desired stress.

@TerranSwett You are confusing cause and effect; you adjust the strain by regulating the load, and therefore stress, applied. What you are saying is that you adjust the force of a spring by stretching it to a set length... well, in that case I'd ask how did you make it stretch in the first place.

@AEheresupportsMonica The causation goes both ways, doesn't it? For simplicity, imagine two balls that have opposite electric charges and which are stuck to each other. If I grab the two balls and apply an outward force to them, they will separate—stress causes strain. At the same time, however, the fact that the balls are separated causes them to exert a net force on each other—strain causes stress. It isn't an infinite regress of causation, of course, but it is a feedback loop. I don't think it's correct to label one as "the cause" and one as "the effect."

@TerranSwett that was the case which I addressed in the penultimate paragraph.


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First Boeing 757-200 N757A 'Catfish' was modified with a Canard foreplane. How did it behave?
The aircraft had these changes made around 2006 to act as an F-22 Avionics test bed. One would expect that the fore plane changed many performances of machine, including take off and landing attitude and behavior. I am interested in knowing more about results of adding the canard fore plane to a series airliner.
A similar arrangement was proposed, it was promissory even at hyper sonic speeds, in a Naval Research Centre in California, for the Space Shuttle.
Source: Airliners.net

My god that looks hideous!

It is... unique... @Jpe61

Hope it stays unique.

As you said, it was added for electronics development, and for the F22, information is probably difficult to find for such a program... Also, the canard is generally useful at high attack angles, which was probably never tested for this 757

That must be the airplane that The Flying Nun uses.

I was aware about comment by BambOo, but no one answered the issue yet, question is about the flight behavior and performance changes due to the Canard on N757A, if any. Or is this an industrial or state secret? This was cited: 'Flowfield Computations over the Space Shuttle Orbiter with a Proposed Canard at a Mach Number of 5.8 and 50 Degrees Angle of Attack', by William H Reuter, June 1993, Naval Postgraduate School, Monterey, California (Nice music festival, that) Blessings +


text:
What is the difference Between Minimum fuel and Mayday Fuel?
what  is the difference Between Minimum fuel and Mayday Fuel ?

Are you asking about FAA regulations? If so, see this question.

The term Minimum Fuel should be used when you currently expect to land with more than the minimum fuel reserves (so everything is OK right now), but any further delay would result in being below minimum reserves when landing. This situation is not yet an emergency and ATC does not need to give you any priority, but they know that keeping you in a holding pattern could result in you declaring an emergency.
The term Mayday Fuel should be used when it is clear that you will land with less than the minimum fuel reserves. This constitutes an emergency and requires ATC to act immediately (this could be priority for landing or diverting you to a different airport, if available).
The ICAO defined both terms in Amendment 36 to ICAO Annex 6 Part I:

4.3.7.2.2 The pilot-in-command shall advise ATC of a minimum fuel state by declaring MINIMUM FUEL when, having
  committed to land at a specific aerodrome, the pilot calculates that any change to the existing clearance to that aerodrome may
  result in landing with less than planned final reserve fuel.
[...]
4.3.7.2.3 The pilot-in-command shall declare a situation of fuel emergency by broadcasting MAYDAY, MAYDAY, MAYDAY,
  FUEL, when the calculated usable fuel predicted to be available upon landing at the nearest aerodrome where a safe landing
  can be made is less than the planned final reserve fuel.


text:
What does "5B3/P" in CFM56-5B3/P mean?
For the CFM56 engine model CFM56-5B3/P, what does "5B3/P" mean?

It's a more specific designation of the general engine. There are lots of variants of the CFM56 in your case the 5B3/P variant:

CFM56-5B3/P: Same as CFM56-5B1, except for increased thrust rating and
  redesigned high pressure compressor, high pressure turbine, and low
  pressure turbine.

The type certificate has the specific info for it as well. There is also lost of info on wikipedia under the -5B series section.


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Under what circumstances does the F-16 and possibly similar fighters deploy leading edge slats?
What does the F-16 (perhaps other fighters as well) use to decide when to deploy leading edge flaps? I would assume angle of attack, airspeed, stick deflection, or some combination of the three, are the main factors.

Technically, F-16 and "similar fighters" have leading edge flaps (LEF) (or droop flaps), rather than slats. The difference is that they don't form a gap between themselves and the main surface when deflected. This makes them usable at high speeds, whereas slats are typically used for low-speed takeoff/landing.
For fighters, the most important use for them is to extend the range of usable angles of attack (AoA), which is important for manoeuvring as well as for takeoff/landing.
For F-16, @Mr R posted some details. I have some info for Soviet fighters of the same generation.
MiG-29
LEFs have two positions, up and down (20°). They are deployed:

When landing gear is down (including takeoff and landing).
Automatically in flight when AoA > 9° and M < 0.8 (Mach number).
On manual override by the pilot.

Su-27
LEF on Su-27 don't have fixed positions and constantly track AoA in flight. Maximum deflection 30°.
They are automatically deployed to 3/4 of travel when landing gear is down for takeoff or landing.
The pilot has a manual override (down-auto-up selector).
For both aircraft, if LEF fail, the allowed AoA is limited to 10°, which is roughly half the normal (depending on speed).

According to a F16 forum..

Those are the LEF's (leading edge flaps). They are there to produce extra lift to the wings during high AOA and low airspeeds. The reason they are up on the ground is they are wired to the left and right main WOW (weight on wheels) switches. They are schedule to -2 degrees on the ground. The only time they move on the ground is during FLCS self test or during LEF ops checks. In flight they are scheduled as a function of AOA and airspeed.

OR AoA and Mach Number (rather than airspeed).

and they actually move up (to form a diamond shape) at supersonic speeds

Same thing happens for flaperons, which means that go up in same way at Mach speed to avoid Mach tuch phenomenon.

Early F-16 LEF schedule according to NASA TP-1538:

It's basically 1.38 times the Angle of Attack, with a lead-lag filter, and then minus 9.05 times Qc/Ps.
Qc/Ps is a rough indication of mach number. So what this control logic actually did is that, the LEF deflection increases with AOA, and decreases with mach number.
If WOW or reaching supersonic speed, the LEF is deflected 2 deg upwards.
For Su-27, the main source is chapter 8.7.8 in the SU-27SK flight manual. Here's a rough summary:
In FLIGHT mode, the LEF are deflected in the range of 0-30° at Angles of Attack of 1°-15°. The relation is basically 2 x AOA.
In TAKEOFF and LANDING mode, the LEF are deflected by a fixed angle of 23°.
When IAS ≥ 860 km/h or M ≥ 1.05, the LEF are retracted. When flight speed decreases, the automatic scheduling of LEF turns back on at IAS ≈ 790 km/h or M ≈ 0.98.

For the F-16 only talk, the wings must be at an angle of attack more than 9 degrees   slower speed or more if you are making a turn but no more than Mach 0. 95 above this value is upward 2 degrees and locked. For the F 16 with TO  /Landing gains(landing gear and trailing flaps _flaperons _at 20 degrees down, the Leading Edge Flaps are  15 degrees down - on speed - if not will vary depending on the AOA or weight on wheels = upward 2 degrees ).

What is your source for this information?


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What medical issues or procedures can cause denied medicals?
Are there a lot of things that can cause a denied medical? Can fairly routine procedures be grounds for denial? (Please don't hate me for having 2 questions in one!)

You will find that there are lots of things that are clear cut, but that most of the potential issues are grey, and require evaluation. The general standard is the risk that a condition can result in physical or mental incapacitation at a bad time. So a procedure that results in little to no risk of incapacitation after recovery, you'll probably be ok, but you have to just disclose it and find out what happens. I've developed sporadic Afib, which is mostly an annoyance, as have no underlying heart disease. I had to disclose it and submit reports. Waiting to find out if I can keep flying.

Got it. I was worried about a few prior injuries but they’ve not been an issue since, and incapacitation isn’t an issue. That’s a really good way of explaining it, so thanks!

Its really no big secret, the FAA publishes their full guide for AME's and you can read it if you like (all 514 pages...) and generally speaking it lists a lot of the disqualifying factors. They offer various guides as well, all of which are public.
If you are worried that something relating to you personally is grounds for denial you can always reach out to an organization like AOPA for assistance.
Routine Procedure is a fairly broad term and an answer cant really be provided since this can be highly case by case depending on what the procedure is.


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Why does the Cessna 208 Amphibian have extra tail surfaces?

Mark Harkin, CC BY 2.0, via Wikimedia Commons

I've seen extra tail surfaces that look like additional vertical stabilizers on the C208 Amphibian. Why is there a need for this? I can't imagine that the floats reduce vertical stab effectiveness.

Well, it's the same reason that the Challenger ultralight demonstrates extreme "adverse yaw" in response to aileron inputs when flown with the doors on, but less so when flow with the doors off.  The floats-- like the doors-- increase the surface area in front of the CG, which has an effect similar to decreasing the size of the vertical fin (which, naturally, is behind the CG.)  "Directional" stability is decreased.
Just like if you took a weathervane and added enough surface area in front of the pivot point, it would stop working.
It's not uncommon for aircraft on floats to have modifications to increase the effective area of the vertical fin, usually by adding a small ventral fin below the fuselage.
Which begs the question-- Why did the Wright brothers take steps to increase the amount of vertical surface area forward of the CG on some of their aircraft?

That makes a lot of sense. Thanks!

When I was a bush pilot one of the minor side jobs besides hauling fishermen and hunters around in a C-185 was doing float ratings in the air service's  Fleet 90 Canuck.  The factory float installation did not include any additional fin area and the Canuck already had a smallish fin/rudder.  On floats the thing had very mild yaw stability and would slither all over the place when maneuvering and you had to be on your feet constantly like flying a glider.  I usually had to give a student taking a float rating about 2-3 hours of dual just flying around getting the hang of the yaw behaviour.

@JohnK: ...How did that installation get FAA approval?

It was certified about 1948.


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How are the wings of the Rutan Quickie constructed?
I’ve read that the Rutan Quickie uses wings which are hot-wired out of foam and covered with fiberglass, but I’ve struggled to find further details. What type of foam are the wings cut from, and are they reinforced/stiffened in any way?

https://youtu.be/p9GTYsNBiaE?t=647

The foam is closed cell polystyrene, like the blue or pink rigid sheets sold at Home Depot.  In later years builders switched to much-more-expensive polyurethane foam because of its fuel/solvent resistance.
The Rutan design just used solid cores split where the spar web goes, with applicable layups of glass/epoxy resin to make the spar web and flanges, and skins.

The structure is extremely simple and quick to fabricate; the time consuming part is the finishing.  To get a finish like a mold-produced part required many many hours of filling and finishing the outer surface.
Builders were attracted to Rutan's process by the apparent simplicity of the construction, but discovered the projects took just as long to complete as a metal or fabric covered plane because of all the finishing hours of sanding and filling.
Epoxy resin can be a problem as well. In the 70s when builders were turning out Vari-Ezes, not much consideration was given to protection from epoxy exposure, until it was discovered the builder could become sensitized to the resin and many had to abandon projects because they would break out if they went anywhere near uncured epoxy once sensitized, protection or no protection.  Nowadays people know to use the proper masks and barriers like gloves and special creams to minimize exposure to epoxy fumes.

And once you are through all that filling and sanding, you could as well use the part as the core of a mold. From that mold you can produce multiple parts which weigh less (no filler!) and are built from the outside in, so you can have useful structure and parts on the inside (pushrods!) instead of a solid foam core.

To be fair, it was intended as a one-off method for the scratch builder back in the pre-kit days.No individual builder was about to build a set of molds.  It helped a lot when builders learned to use peel ply and vacuum bagging for layups.Peel ply gets you way closer to the finished product, more or less the surface roughness of the dacron peel ply fabric molded into the resin, and cuts the sanding and filling back drastically as long as your cores were cut accurately. A chum bought a Dragonfly, whose cores were not quite so precise, and micro-filling and sanding wore him out and he sold it.

the quickie wing is indeed a foam core with a fiberglass resin skin. it is reinforced with a single spanwise fiberglass web protruding down from the top surface of the skin into the interior of the foam core, which is securely glued to the underside of the skin.


text:
Do the stabilators on the F/A-18 also have a roll function similar to the F-22?
I'm curious about the F/A-18C. I know it has ailerons, but they seem too small to be greatly effective at low speeds. Do the stabilators have a roll function as well? If so, is there a speed at which one or the other becomes inactive?


text:
Locked out of private jet - how do you get in?
Ok I'm not a jet owner, I'm a novel writer. I wanted to get my airplane facts right for the story.
Say my character has a mid-size (can go overseas) private jet. Has a door lock on the outside door and cargo bay. The bad guys stole his keys, so now he's locked out. My character is a pilot and is with a friend who is a jet mechanic. If the mechanic has tools, and 24 hrs, would they be able to get in to their jet and fly it?
If so, how would the mechanic go about getting in (while leaving the aircraft in flyable condition)?
Or would the characters need to call a locksmith?
I was thinking pretty high in the sky (I was going to have the mechanic literally unscrew the door and then put it back on) but then I thought I'm probably being unrealistic and I should ask someone who's actually worked with jets.

Welcome to aviation.SE! Does this question help?

Actually that's one of the posts that I read that did help me, initially. But it didn't answer how to get past a door lock if a jet DOES have one.

If your pilot is really smart, he’s done what I do and hidden a key under an inspection plate or fairing—but that isn’t very MacGyverish.

He calls the regional service center, asks for a service call to open his plane up along with a replacement key (or remove and replace the locks so he gets a new set of keys; his are compromised).  He pays whatever it takes since he is wealthy enough to own a private jet.  They fly to his location, perform the work, and leave in way less than 24hrs.

@acpilot Plot twist... the bad guys intercept the call and send out their own guys...

Our protagonaist knows that they would intercept the call and prepared a trap. Knowing that the bad guys would show up as the mechanics, he invited the FAA to do a practice ramp inspection at the same time. The bad guys had no choice but to unlock his plane or else risk answering questions from puzzled FAA inspectors. They would be unable to cite details of their part 145 repair station manual or answer simple questions about airplanes. As the owner boards his plane he does his signature move: chucks a fist full of dollars into the air and shouts his tagline, "keep the change, sucka'."

@Angela you may find https://worldbuilding.stackexchange.com/ very helpful and interesting.

Does the protagonist need to fly the plane away without sacrificing his discipline as a law-abiding pilot? Perhaps an easier act of sabotage with the same effect would be something at the airport-level that would prevent ATC from clearing the jet for take-off.

Assuming the bad guy plans to use the aircraft later, otherwise he might've just torched it.  Consider that the aircraft wasn't locked but disabled. Take a look at a  Learjet 45 manual and see if anything inspires you: http://www.figueroa.net.br/Manuais/Learjet-45.pdf

@acpilot: plot twist: owner is actually Kevin McCallister, of "Home Alone" fame, so his tagline is, "Keep the change, ya filthy animal".

@Angela Big question: when and where are you releasing this story? And can participants here get a discount?

You guys are so fun! Sadly, I am only self-publishing this one; it turns out that it's not going to be quite long enough to be considered a full-sized novel (word count is a thing with publishing companies). So I'll be putting it on Amazon Kindle, hopefully in the next few months. Don't worry, it'll be cheap enough not to break the bank! Maybe I'll let you get it for a dollar or two. ;-)

Hammer and (not) nail

After hours, I once climbed up into a B-24 parked outside a museum and had free run of it.  Hope this helps answer your question.

It depends on the exact model. Bobby pins or any key that physically fits will get you into some, you'll need real picks for others, and some custom jobs may require a police snap gun or a locksmith's services. This doesn't correlate with aircraft price: the larger and more advanced, the less likely it is to have any locks at all. At the high end, jumbo jets have no locks and have a (not so) convenient hatch in the gear well, so you can climb inside even without a ladder.
Mechanical locks, with the exception of the more robust types used on burglary-resistant safes and vaults, offer only very superficial security. Airplanes are protected against professional threats by external access restrictions (fences, hangars, guards). When parked at a small local airport, opportunistic theft is deterred by "security through obscurity": very few people are able to operate one, with model-specific skills are involved, and even fewer could make use of a stolen jet. Unlike car parts, aircraft parts come with paperwork.
The locks used on most aircraft doors are small pin and tumbler cylinder types that can only protect against passers-by. The stock locks on the most popular light planes even use wafer tumblers, which offer no resistance to picking - some light bumping with a key from another lock of the same type will get it open. Quite a few owners have opened plane doors with a wrong key by accident.
If you're not concerned about property damage, as in an emergency situation, no picking skill is required to open the kind of locks you'd find on a private aircraft. A non-matching key or a flat-head screwdriver, jammed into the keyhole and forcefully rotated with a pair of pliers, can break small cylinder locks' pins and allow the lock to open. Larger locks require a bit more effort, but it's all fairly intuitive work of destroying what's in the way of opening the latch.
In non-pressurized aircraft, you can also bypass many locking mechanisms by applying well-directed force, which slightly deforms the door to allow the latch can exit the door frame. In some cases this can be done non-destructively, just by elastic deformation. Pressurized doors fit too tightly for this, but the lock is still a standalone device, not tied into the door's operating and sealing mechanism, so damaging it won't leave the plane inoperable.
24 hours is far more time than would ever be needed. 1 hour is enough time to get a professional locksmith, which, with proof of ownership, can get you into any stock aircraft/boat/car/other vehicle with usually no damage to the lock. Another hour will get you a new set of keys, or a change of locks with new working keys.
The time it takes to get into a locked aircraft, in an emergency situation, should be between 20 seconds and 20 minutes, depending on the plane, the characters' skills and equipment, and their willingness to damage the lock. For a larger jet you'll definitely be going after the lock, not the door.
The only entry-resistant doors in aviation are those separating airliner cockpits from the passenger cabin, with electronic locks and solid locking mechanisms. They're rated against different threat models than UL vault doors, but my best estimate based on their construction and weight would place these doors at around TL-15 level, with about 15 minutes of power tools resistance.
For reference, the highest ratings for safes and vaults are TRTL-120 and TXTL-60, indicating 120 minutes contact time resistance against power tools and torches, or 60 minutes against explosives and small thermal lances. In absence of a security response, 24 hours and a good hardware store can get you into Fort Knox.

Comments are not for extended discussion; this conversation has been moved to chat.

"In absence of a security response, 24 hours and a good hardware store can get you into Fort Knox.".  This is what so many people forget, that physical barriers on stationary objects are deterrents, not the final solution.  Proper security modelling determines the maximum response time of the means to remove the attackers from the barrier, and makes sure the response team (e.g. police) are alerted.  If the barrier holds up during the response time, it did its job.

@madscientist159 Anecdotally, I worked at a place once that had doors with ratings for how long it would take to penetrate them. So the rooms they protected would require "at least X time" before gaining unlawful entry. The point was to just provide sufficient time for security to respond given an alarm event, which would likely be going off in the event of a real attack on the door.

Yeah, sure, that's great - but how do you get the hardware store to Fort Knox?!?!?

The only key lock you might encounter on a corporate jet will be a pin/tumbler lock securing the outside operating handle of the main entry door.  You won't find anything exotic unless the owner has gone out of his way to install something. Just about all pin tumber and disc detainer locks can be picked fairly easily with some skill and practice and the right picking tools (an electric picking rake or a snap gun makes it so easy pretty much anyone can do it).
This guy's Youtube channel shows how easy it is to defeat most locks, even the most sophisticated "pick proof ones", EXCEPT for one lock that has defeated him so far, called the Bowley lock.
Beyond that, there will be no internal locks you have to worry about.  Just oodles of switches.

Awesome! I had never heard of a snap gun. I'm looking it up and I'm like, hey! Now I want one!

That thing about the switches reminds me of the lock set where the attacker can lock and unlock any given lock in the set at will... only they can't tell whether a lock is locked or not (you can't see the bolt and some are reversed so turning in one direction may lock or it may unlock), and there are around 30 locks on the door.

Lest this turn into an advertisement for Bowley locks: https://www.youtube.com/watch?v=X04qgD0hOXk&feature=youtu.be - good but not unpickable

@abligh True that. There are no undefeatable locks - there are locksmiths that haven't learned how to work a particular type. And non-locksmiths get to spend way less time actually working the locks.

Snap gun, I ways

There are a lock-picking videos on YouTube - search for "Bosnian bill" and "lockpicking lawyer". There's a third series, but I can't remember the name at present.
These guys make light work of almost all locks

Another possible way in would be through the emergency exits. Emergency exits are designed to allow them to be opened from the inside or the outside in case rescue is needed.
Many planes that I fly have a pin that is engaged inside the cabin that is to be used when the jet is parked and removed for flight.
In almost every case, the pin is virtually never installed, even when the aircraft is parked on the ground.
So, our hero could open an emergency exit, close it, and take off assuming the locking pin were not installed.

Most operators will have a policy that this pin is to be installed. I personally ensure that the emergency exit is properly pinned every time I leave my jet on a ramp overnight.

Here's a very much non-aviation-approved solution which may be attractive in that it allows a McGyverish solution to an aircraft with a more than usually resistant lock design.
If "safely flyable" rather than "certified flyable" is acceptable, then cutting any suitable window along a line say 10mm+ from the edge and gaining access via the hole would in many cases be a possibility.
If there are on site repair services available and able to perform a replacement in a suitable period, use them. If not ...
Such a hole can be repaired "with ease" [tm] by applying a sheet of glass (or indeed any suitable strong sheet material) to the window's inner surface and bonding it in place with a "fast enough" setting silicone rubber or other adhesive. Differential pressure would serve to enhance the bond. Silicone rubber is very adequate for this task and many alternatives would be too.

Really "just for fun" - make the story interesting.
Could I cut a hole in the windscreen and fix it this way ? !!! :-)
Window pressure from airflow at sea level on a surface at right angles to the flow is not more than
F ~~ 0.6 x A x V^2
A = area m^2, V = velocity m/s, F = newtons
Or, per square meter - F = 0.6 x V^2 newton
At say 100 m/s = 360 kph
P = 6000 N = 6 kPa.
Atmospheric pressure at sea level = 100 kPA.
At say 14,000 feet Pa ~= 50 kPa.
I'll not attempt to work through that numerically or to refine the assumptions, but it seems doable. Under some circumstances an external windscreen patch may be preferable.
Noting that the edge bond forces, if inwards, increase with the square of the linear edge size. but bond force increases linearly with edge size.
Suitable juggling of Pinternal and altitude may allow an interior patch a relatively low stress ride.
I'd not consider trying it.
McGyver just might.

Getting into a private jet would be the easy part. Safely taking off in a jet in which you are not familiar is hard. Taking off in a private jet without arousing suspicion would be way harder. Especially if the jet were based at that particular airport. Most private jets are not hangared at airports small enough not to be towered and/or attended.
A fast and capable prop would be more likely.

I would disagree about the difficulty. Taking off, especially for an already-certified pilot with access to the checklist, would be about the same as any other aircraft. Just faster. And unless the tower knew the owner of the jet, semi-competent radio work would allay much suspicion. Once in the air, flying is pretty much flying. However, LANDING an unfamiliar aircraft would be quite a bit more problematic.

Sorry, I should clarify that the difficulty in taking off is not in the piloting skills. It’s in the getting-away-unnoticed skills. The private and business jets based at the Class D airports in our area are mostly hangared. People who are either employed by the airport or residents, and the regulars (affectionately known as hangar bums) at the airport are walking around the area all day. We are such a good-neighbor community that we and ATC even recognize the voices of pilots on the radio. A new face and voice does not usually go unnoticed.

authors: Bob Jarvis - Слава Україні


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Has a wingsuit pilot ever flown inverted for an extended period of time (say more than 5 seconds)?
Has a wingsuit pilot ever flown inverted for an extended period of time (say more than 5 seconds)?
(Additional content added to add length to "meet our quality standards") --
It seems it should be possible.  But perhaps it would be too disorienting.  Or perhaps the suit is made to curve in a certain way that is not compatible with sustained inverted flight.

Red Bull (who else?) did it: Umgedrehter Wingsuit-Flug über die Dolomiten (inverted wingsuit flight over the dolomites).

It looks to be around 10 seconds. Parts of the video are in slow-motion, but this part does look real-time.

It's working much weaker muscles across the back and triceps. It doesn't look like he can hold it more than maybe 10 or 15 sec.

Not just the muscles, even relaxing the chest the arms only go so far back falling/gliding face down.  (you can't easily clap your hands behind your back!)  While backwards the full force of the air would be trying to push your arms together in front of you...


text:
Is it a bad idea to brush your teeth with water from an airliner sink faucet?
Is it a bad idea to brush your teeth with water from an airliner sink faucet?  Does some sort of health risk from said water outweigh the risk of poor dental hygiene?

this question is informed by something I heard on the radio today.

This might be related info

There is often a queue for the lavatory, so think about other passengers before taking it potentially for much longer than a typical visit requires.

It belongs to travel.se

The question this is marked as a duplicate of seems barely related, let alone a duplicate.

There might not be a generally valid answer, it depends on the airline and the departure airport. Here's a newspaper article in German (translated).


text:
Do the rules used in modern soaring competitions forbid gyroscopic flight instruments, or forbid the use of AHRS-driven attitude displays, etc?
In the past, the rules for soaring competitions in the US and many other countries have not permitted gliders (sailplanes) to have working gyroscopic instruments installed, to prevent pilots from being able to "cheat" by continuing their thermal climbs into clouds in violation of the relevant air regulations and/or the rules in place for the contest.
(The hazard of putting dozens of gliders into the same cloud is obvious, hence cloud-flying was sometimes banned by competition rules even in nations where it was permitted by the air regulations.)
As a result of these rules, in the past it was not uncommon to see a glider at a contest with blank hole in the instrument panel where the turn rate indicator had been temporarily removed.
But an ASE answer has stated

These days, AHRS is dirt cheap, and it is available on many common
flight computers and varios.

Here are images of a variometer1 with an AHRS-driven artificial horizon display2--

Butterfly variometer in variometer mode

Butterfly variometer in attitude indicator mode
This advance in technology naturally raises the following questions--
Do the rules used in modern soaring competitions still ban dedicated gyroscopic flight instruments such as the old-style mechanical turn rate indicator and attitude indicator?
Do the rules used in modern soaring competitions forbid the use of instruments with the capability of displaying a simulated "attitude indicator" driven by means of AHRS (artificial horizon reference system)?
If an instrument with such a capability is allowed, is there a requirement that the attitude indicator display not actually be used, i.e. that that particular display screen not be selected in flight?
If so, would the selection of that screen be "flagged" in some way such that it will be known after landing-- similar to if a motorglider uses its motor during a contest task?
A close look at the website that is the source of the images included in this question reveals that in the particular case of the "Butterfly" variometer, the articial horizon display "can be deactivated in a tamper-proof manner".  Is such deactivation actually required by the rules in place for soaring contests?
Basically I'm asking if, in soaring contests where the rules prohibit cloud flying, there's anything other than "the honor system" in place to prevent pilots from using a modern variometer featuring an AHRS-driven attitude indicator display to "cheat".
Are the flight tracks evaluated afterwards and compared to the forecast or reported cloud bases?  That would seem to allow for at least a thousand feet or so of "cheating" due to variations in cloud base over time and space--
My question is not meant to be specific to the USA, but answers should note which nation they are describing.
Any rules that apply to record attempts, badge flights, etc rather than to actual contests would also be of interest.
I'm asking specifically about sailplane competition, not hang gliding or paragliding.
Footnotes--

The primary reason that AHRS systems began to be integrated into sailplane variometers was to facilitate the use of accelerometers to provide faster detection of changes in vertical speed than would be practical with an instrument purely based on changes in atmospheric pressure.

Source of images-- "Craggy Aero" website

Some other related ASE questions and answers of interest--
Can you fly a glider in a cloud on primary instruments?
Can you fly a glider in a cloud on primary instruments?
Can you fly a glider in a cloud on primary instruments?
In what airspace may gliders fly in clouds in the UK without an IFR flight plan and without contacting any air traffic control facility?
Other resources of related interest--
"Teaching Instrument Flying"-- Instructor Training Notes-- Dartmoor Gliding Society -- note the comment on page 1, "It is recommended that an ‘Attitude Indicator’ is not used for initial training because this leads to over reliance on a single instrument."  As hard as it may seem for today's pilots to believe, there is a long history of cloud-flying in sailplanes, especially in European countries and Great Britain, relying on a turn rate indicator as the sole gyroscopic instrument.  Older books such as "New Soaring Pilot" by Welch, Welch, and Irving (3rd ed 1977) discuss this practice in detail.
"Instrument Flying Training Notes"-- Dartmoor Gliding Society -- Note the comment on page 3, "The use of the AI is not included within this course."
Cloud Flying endorsement webpage from Motorglide.co.ok

This is a real question-- not intended to be self-answered-- although I'm an active soaring pilot, I'm not involved in competition nor have I flown w/ these newfangled gadgets...  I have people I could ask, though, so a self-answer may eventually be provided if none other is forthcoming--

@JohnK -- Based on your answer, I've made edits to the title and to the body of the question to try to clarify the intent of the question-- the point is not "hey, I've thought of this thing I'd like to do and I'm wondering if the rules allow it", but rather more along the line of "I know this has been an issue in the past and I'm wondering how the solution used in the past has been adapted to deal with recent changes in technology."

As I'm not a competition sailplane pilot, I can't answer all your questions.  The Soaring Society of America (SSA) sets rules for soaring competition.  The newest version of the rules (2021) state:

6.6 Restricted Equipment
6.6.1 Each sailplane is prohibited from carrying any instrument that
-Permits flight without reference to the ground
-Is capable of measuring air motion or temperature at a distance greater than one wingspan

There is a supplemental document from 2012 describing possible waivers:

By waiver, the Rules Committee may allow the installation of such a device if the RC determines that the “artificial horizon” or “turn and
bank” capability can be effectively and verifiably disabled for the
period of the competition.

The rules and supplemental documentation can be found here: https://www.ssa.org/ContestRules

Welcome to aviation.SE! Please use the quote markup (the quote signs in the editor) for quotes; that helps people who use screen readers, for example.

At a very basic level, VFR flight, whether it's power or glider, in any normal jurisdicton, requires cloud clearance laterally and vertically, and there's no exemption from national VFR regulations for glider competitions in any universe I know of.  When soaring on a normal day, you are technically violating national VFR cloud clearance regulations just by nestling up into a cloud base at the top of a thermal.
So from a practical perspective, it's simply illegal unless you are on an IFR flight plan, in an aircraft equipped with the certified minimum equipment, which a glider with AHRS falls far short of.  I don't know how a soaring organization in any Western country could authorize a deviation from basic aviation regulations like that.
Plus at a very basic airmanship level, intentionally flying around in cloud just for fun, without the specific training required to do it safely (you know, actual instrument flying training), is just crazy, and old practices doing that sort of thing in Europe or wherever in the past doesn't make it any less crazy.

Actually this answer would be better suited to a question more like this one-- https://aviation.stackexchange.com/q/26808/34686

Your answer also begs the potential ASE question "Is there a minimum equipment list for cloud-flying in gliders?"  (Say, in the US)

My answer responds to your 4th last para.  Your question is not relevant because it relates to an activity that is illegal in the first place except as an escape from trouble.  At least in North America.

A) why should illegal activities be outside the scope of ASE questions and B) the question specifically stated that it was not limited to North America.

@JohnK FAR 61.3(e)(3) says it’s at least theoretically possible to fly IFR in a glider.

Under european SERA, it is possibble to fly inside clouds with gliders. In short: this requires some special training, instrumentation, and a flight plan, none of which are "full IFR" as in powered flight. This, to some extent, invalidates this answer.


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If I have the Covid virus, should I consider using O2 at all altitudes while engaged in GA aviation?
If I have the Covid virus, should I consider using O2 at all altitudes while engaged in GA aviation as PIC?  To combat decreases in physiological functioning due to the virus?

Shouldn't you just stay on the ground until you're over it?  Or are you talking about having had a severe case and  recovering but with lung damage?

This seems like a medical question, not an aviation one. The answer might also be different for different people. Although personally I'd say that if you're even asking the question then you shouldn't be flying.

The bigger problem is you’re endangering anyone you’re with.  A masked person who has COVID (e.g. but doesn’t know it) will not spread it to others; their mask stops it.  That is why it is so important everyone wear masks.  However this fails if the mask has an exhalation valve, which I bet your mask does.

IMSAFE
If you have an illness (especially one that requires medication, or puts stress on your body, or causes a decrease in performance, or induces fatigue), you should not fly as PIC. For your own health and safety, you should probably not fly at a reduced cabin pressure at all until cleared by a physician.


text:
How turbofan engine efficiency increases over altitude or speed?
I am confused a lot about the efficiency and thrust relation with altitude and velocity of an  aircraft.  If thrust is related to air mass flow and velocity diffrence of bypassed air - exhaust gases and intake air velocity, then thrust will decrease as altitude increases which is true as CFM56 stationary thrust is 140kN while at cruising altitude it is 24kN. Everyone points out that the efficiency is higher at higher altitudes, but how?
Yes fuel flow decreases too to maintain O/F ratio but what about the reduction of thrust?   Does propulsive efficiency goes higher too? And how the aircraft can still maintain its speed with 1/5 of the thrust at TO,  someone also pointed out drag actually increases with higher altitude and speed, is it true?

Related question about cruising altitude


text:
What are the oxygen requirements for an IFR flight eastbound on V520 from DBS VORTAC in an unpressurized aircraft at the MEA?
IFR written test question by the FAA. Available answers:

The required minimum crew must be provided and use supplemental oxygen for that part of the flight of more than 30 minutes, and the passengers must be provided supplemental oxygen.
The required minimum crew must be provided and use supplemental oxygen.
The required minimum crew must be provided and use supplemental oxygen for that part of the flight of more than 30 minutes.

Apparently the correct answer is 2? MEA is 15,300FT... I don't understand why passengers don't need oxygen.

The MEA is over 14000, so crew members must be using oxygen at all times. This means that both 1 and 3 are wrong. By process of elimination, 2 must be the correct answer.
A better answer to this would be "The required minimum crew must be provided and use supplemental oxygen, and the passengers must be provided supplemental oxygen." But answer 2 is not wrong, it is just incomplete. When choosing between an incomplete answer and a wrong answer on a multiple choice test, you need to pick the incomplete answer.

@user2605553 this is yet another case of FAA trickery I described in my answer to your other question

And the extra info ("eastbound" - so westbound won't be an issue?) is also meant to confuse you. Standard multiple-choice question construction.

@JonCuster Westbound from DBS on V520 has a lower MEA and actually would change the answer in this case.

IIRC, there was a question recently about whether there were any commercial flights with passengers where passengers normally required oxygen during regular (not emergency) flight. And on that basis - i.e., it hardly ever happens, especially as high as 520 because few planes fly that high in the first place - the "passenger" part is basically irrelevant.

@manassehkatz-Moving2Codidact It may be irrelevant commercially, but GA flights can and do go above 15000 feet in unpressurized aircraft.

@Chris True. The question is how often do they do that with passengers and without pressurization.

@manassehkatz-Moving2Codidact The answer is sometimes. ;) It's basically the mission that turbocharged unpressurized airplanes were designed for.

The thin air at 15,300 feet isn't dangerous to healthy individuals -- mountain climbers routinely climb summits higher than that without supplemental oxygen -- but it really messes up your decision-making.  The crew need to be thinking clearly, so they need to be on oxygen, but the passengers are't making any important decisions.

Not disagreeing with your explanation, however passengers are required to have supplemental oxygen above 15,000 ft. As pointed out in the answer by @Chris the correct answer in the FAA exam (#2) was an incomplete statement. Likely a trick question, designed to catch someone who remembered the 15,000 limit for passengers and thus assumed answer #2 was wrong and went with answer #1 because they didn't remember the 14,000 ft. limit for pilots.


text:
IFR to VFR Flight Plan Change
A pilot has filed an IFR flight plan.  While airborne, he feels like changing to VFR flight. Can he request for it and what are the conditions?

Yes, if in VMC a pilot can cancel IFR, then request VFR flight following for the remainder of the trip.

Yes, but requesting flight following is always optional.


text:
What is the difference between an Instrument and Equipment?
In an aircraft, what things is an instrument and what things is an equipment? For example the ILS, is the Antennas located in the runway considered to be an instrument or an equipment? Or is there another example to differentiate both?

Not all equipment are instruments. The voice radios for instance are definitely equipment, but they are not instruments.

"Equipment" is a very broad term and it covers more or less anything physical, e.g. the "equipment list" for a light Cessna includes the paint. "Instruments" are things that display measured information to the pilot in some way: altimeter, airspeed indicator etc. But that's just my opinion; words change their meanings in different contexts, and I'm not sure what context you're asking about. But if you don't get a useful answer here, you might try english.SE.

All instruments are equipment, but not all equipment are instruments.

In the aircraft an instrument is related to equipment providing displayed data.

I disagree that long answers are better.  Sometimes a concise clarification is all that is needed.  A long winded overblown answer to very simple question is unnecessary, and can actually drive readers away.


text:
How do you indicate whether the supply of power to the gyroscopic instruments is adequate?
Is there an instrument to indicate this?

What type of aircraft are you interested in? The instrumentation of a new airliner is different from a glider, or a 1930's biplane.

@DanHulme Would like to know what the commercial plane use

All the types of aircraft I mentioned are flown commercially. Are you asking specifically about airliners?

For suction powered gyroscopic instruments there is usually some suction gauge to indicate the quality of the vacuum. See this question for more details in what the instrument shows.


text:
What does "Where AOC requirements are redundant to AAC requirements, or more detailed, the AOC requirements will be followed." on Part 7 of CAR
Does it mean, The requirements for AOC are no longer useful to AAC, AOC will be used?

It means that if the AOC is more detailed, or contains the same thing as the AAC, then whatever is written in the AOC should be used.


text:
Why are some vertical stabilizers painted 'after' installation?
I recently watched the Airbus videos on making the first PAL and Air China A350s. PAL’s vertical stabilizer was painted before being installed, as explained in 'Why are the tails always painted, but not the fuselage, in test and delivery flights?'.

But Air China’s (MSN 167) was painted with the fuselage (after installation). This confused me because I have been told that painting the vertical stabilizer is for balancing the rudder.
What factors affect when the rudder is painted?

A photo for MSN 167 confirming what was seen in the video. (flickr.com)

Possible duplicate of Why are the tails always painted, but not the fuselage, in test and delivery flights?

The most important safety consideration when painting the tail of an aircraft is balance of the flight control surfaces to prevent flutter. This means painting of the stabilizers can happen whenever the manufacturer finds it most convenient, since they are not flight controls.
Flutter begins when the support structure of a flight control is displaced and the control is unbalanced, ie. heavier behind its hinge line. In an aileron, which is the flight control most sensitive to flutter, a gust might displace the wingtip upwards. The unbalanced aileron, heavy behind the hinge, deflects downwards due to inertia. This increases lift amplifying the effect of the gust. When the structure flexes enough to reverse the excursion of the wing, the aileron continues to rise due to inertia and deflects upwards. This reduces lift on a wing that is already descending, amplifying that motion. Uncorrected, this develops into an oscillation of increasing amplitude until structural limits are exceeded and the structure fails.

One less efficient way to deal with the weight of paint is to overbalance the flight control, meaning make it heavier ahead of the hinge line. This prevents flutter from developing because all the inertial effects on the control run counter to the deflection of the supporting structure. It is less efficient because there is unnecessary weight in the control, but it does mean that you could theoretically calculate paint weight and add some margin to ensure that overbalance is maintained after painting. Airliners don't take that theoretical route due to regulation and desire for efficiency.
Painting/repainting of the rudder, elevator and ailerons in commercial airliners always requires balancing of the control surface. This means that the mass of the control ahead of the hinge line equals the mass behind the hinge line. On a b737, the rudder can be balanced while installed on the aircraft. The horizontal stabilizer can also, but in a more restricted manner. Ailerons have to be removed, as they are most sensitive since their support structure (the wing) flexes far more than the aft fuselage where the other controls are located.
For both your aircraft all the controls will be balanced prior to flight. The A350 apparently allows balancing of the rudder while installed on the aircraft, just as the B737 does. This means it does not need to be painted prior to installation, and the manufacturer is indifferent to any cost differential.


text:
Which was the first "business jet" equiped with supercritical wing?
Supercritical wings are common in today's large aircrafts. Looks like the Vickers VC10 was the first airliner using this wing but I didn't find anything related to small jets. I've been told that the CL-600 was one of the first business jets mounting such wing, I also heard that the Dassault Falcon 20 holds that honor. Which was really the first "business jet" equiped with a supercritical wing?

The Falcon50 beat the Challenger by two years.
One price of the early SC wing used on the Challenger was terrible stall behaviour. They suffer from a leading edge bubble formation which causes the entire wing to stall from the leading edge. The Challenger and its CRJ descendants have to have stick pushers because of this, because the natural stall flaps up (all flap positions for those without LE slats) must be prevented at all costs.
The Falson 50 avoids this and needs no pusher, but I'm not sure how.


text:
At what altitude should I join overhead a fix when my legal MSA is lower than the holding altitude?
For example, if my MSA is 4600ft and the holding altitude is 6500ft, am I legally allowed to join overhead the fix at 4600ft, or do I need to join overhead the station at 6500ft?

Can you clarify what MSA means in South Africa?  In the US it is a sector altitude that will provide 1000' of obstacle clearance or 2000' in mountainous areas.  In this case it looks like there is a 4600' mountain west of the field, and an MSA of 4600'.  Zero clearance in other words.  Am I interpreting this correctly?  Because you really don't want to fly in IMC at 4600', in any sector...  (and it's 7300' to the East!)

@MichaelHall It sure looks like the SA protocol is that the MSA presented is the actual maximum terrain level for the sector and leaves it to the pilot to factor in obstacle clearance.  I tried hunting around for SA approach chart conventions but struck out.

@MichaelHall MSA in it's respective sector will give you 1500ft clearance over obstacles in South Africa.

@Skydemon, ok... but what does "46" mean on that thing that looks like a mountain 10nm West of the VOR?  Is the terrain actually 3100' so that you can fly over the top of it at 4600'?


text:
How to determine when a non precision approach does or doesn't have a Final Approach Fix (FAF)?
I am curious to know how to know for sure whether a non precision approach has/doesn't have a final approach fix by looking at its plate. From what I can see, a Break Cloud and/or NDB procedure might not have a FAF, but I am not 100% sure.
Can anybody give me an example of a NPA with FAF and NPA without?
These are two examples of NPA plates from South Africa.

Although we have NDB IAPs in the USA, they are becoming more and more rare. I know of no Cloud Break approaches. As a matter of fact, I don’t know of any approaches that do not have FAFs. Are these common in other countries? Were there ever any Cloud Break approaches in the US in the past?

These are quite common in South Africa. There are some Approaches without FAF's here, but I'm finding it hard to determine which ones they are.

Cape Town is in my top five favorite destinations. Post more approaches like this or links to where they can be found when you find them. The closest I can find to these in the US is our Visual Climb Over the Airport.